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Yoga and The Nervous System
The human body has two subdivisions of the nervous systems, the somatic and the autonomic. While the somatic nervous system is responsible for voluntary control of body movements, the autonomic nervous system regulates involuntary physiological processes (such as blood pressure, heart rate, body temperature, digestion, urination, and metabolism). Within the autonomic nervous system, there are two main divisions, the sympathetic and the parasympathetic. When the autonomic nervous system receives information about the body and the external environment, it either stimulates body processes (through the sympathetic nervous system), or inhibits body processes (through the parasympathetic nervous system).
Each autonomic nerve pathway involves two nerve cells. One of the cells is in the brainstem or spinal cord, and the other is located in another area of the body in a cluster of nerve cells (called an autonomic ganglion); the two are connected by nerve fibers. Nerve fibers from the ganglions connect with internal organs. The majority of the ganglia for the sympathetic division are located on both sides of the spinal cord. The majority of the ganglia for the parasympathetic division are located near or in organs.
The sympathetic division of the autonomic nervous system prepares the body for fight, flight, or freeze, whereas the parasympathetic division of the autonomic nervous system controls the body processes in ordinary/non-threatening situations. When the body perceives that it is in danger, the sympathetic division is activated; our heart rate increases, our body releases stored energy, our muscular strength is increased, our palms sweat, pupils dilate, etc. In this process, our slower body processes (that we do not need to survive in that moment), such as digestion and urination, are slowed. When the body feels relaxed and anxiety-free, the parasympathetic division is activated which works to conserve and restore. In other words, our blood pressure drops, heart rate slows, the digestive tract is stimulated to process food and eliminate waste, and the energy that we get from digesting food is used to restore/build tissues.
Any time that we are breathing more than roughly 10 breaths a minute, our sympathetic nervous system is activated. When we can keep our breath below 10 breaths a minute, we are able to activate our parasympathetic nervous system. Because of the rapid nature and high-energy, high-stress lifestyle that so many people live today, the majority of the time our sympathetic nervous system is activated. As you could guess, this can lead to many chronic problems such as poor digestion and high blood pressure. And that is why it is important that we practice yoga.
Through a regular yoga practice, we are able to increase our respiratory efficiency. With greater respiratory efficiency, our respiratory amplitude and smoothness increase, tidal volume increases (how much air you take in in a normal breath), vital capacity increases (how much air you expel after your deepest possible breath), and breath-holding time increases as well. Through taking in fuller breaths, and having more control over our breath, we are able to train our bodies to breath less breaths every minute, and intentionally take ourselves from the sympathetic to parasympathetic nervous system on command.
It’s not bad or wrong to be functioning from your sympathetic nervous system. In fact, we all need to in order to survive! It’s what gets us out of the way when a car is coming towards us on the street and we have to swerve, it’s what allows us to stick up for ourselves in a heated argument, and it’s where we get our strength while exercising. However, to be optimally well, we must learn how to mediate between the sympathetic and parasympathetic, and to have more control over when they activate.
This article was written by Haley Lovejoy of A.G.A.P.E. Wellness.